SQL查询的一个问题？

select 区域,诺西=sum(case when 厂家='诺西' then 1 else 0 end),
            华为=sum(case when 厂家='华为' then 1 else 0 end)
from tb group by 区域

select
  区域,
  sum(case 厂家 when '诺西' then 1 else 0 end) as 诺西,
  sum(case 厂家 when '华为' then 1 else 0 end) as 华为
from
   tb
group by
   区域

select 区域,sum(case when 厂家='华为' then 1 else 0 end) [华为],
       sum(case when 厂家='诺西' then 1 else 0 end) [诺西]
from tb
group by 区域

if object_id('tb','U') is not null
   drop table tb
go
create table tb
(
 区域 varchar(10),
 厂家 varchar(10)
)
go
insert into tb
select '龙泉','诺西' union all
select '高新','华为' union all
select '高新','诺西' union all
select '高新','诺西' union all
select '高新','诺西'
go
declare @str varchar(max)
select @str=isnull(@str+',','')+'['+厂家+']=sum(case when 厂家='''+厂家+''' then 1 else 0 end)' from (select distinct 厂家 from tb) t1
exec('select 区域,'+@str+' from tb group by 区域')
go
/*
区域         华为          诺西
---------- ----------- -----------
高新         1           3
龙泉         0           1

(2 行受影响)

*/